Generally, tamper-evident bottle closures comprise a lower shoulder or skirt portion of the closure which is in some way intended to fracture or break upon dislocation (i.e., removal) of the closure on the container, so that it becomes evident that the container has been tampered with or opened. In the past, a large number of these closures have been produced, many on a commercial basis, on various containers including carbonated beverage bottles and other such containers maintained under significant pressures. Up until quite recently, metal closures predominated this field, such as those disclosed in U.S. Pat. No. 3,812,991. However, a series of prior inventions for alternative tamper-evident closures, such as set forth in U.S. Pat. No. 4,343,408, which are assigned to the assignee of the present application, have been quite successful in replacing such metal closures.
In this regard, these patents disclose several commercially significant improvements for such plastic closures for bottles and containers which are designed to include a tamper-evident feature. These inventions have been quite successful in capturing a significant share of the tamper-evident closure market. They have thus provided for the closure to be removed from the container cleanly and efficiently, obtaining a highly reliable fracture of the lower skirt portion. Furthermore, commercial closures have been provided thereby which can be applied in a simple, single step to a container or bottle.
A further improvement on these closures is set forth in U.S. Pat. No. 4,461,390, also assigned to the assignee of the present application. The improved devices disclosed therein include juxtaposed parallel intermediate side wall surfaces which assist in maintaining the upper and lower intermediate side wall portions in alignment with each other upon collapse of the frangible bridge means as the closures are applied to the containers. Thus, a more efficiently operating system is disclosed therein. Again, all of these closures have been and are highly successful.
In yet another such patent assigned to the assignee hereof, U.S. Pat. No. 4,479,586 relates to the inclusion of means for insuring that the portion of the closure which remains on the container after the closure has been removed now separates from the upper portion of the container so as to visibly reveal the fracture thereof. This is accomplished by including an inwardly directed non-locking tapered surface on the container itself which causes the depending lower skirt portion to move downwardly along the non-locking tapered surface away from the annular collar portion of the container when the closure fractures, thus providing visual evidence of either tampering or opening.
Most recently, a further improvement to tamper-evident closures is set forth in U.S. Pat. No. 4,669,623. This closure interacts with the container itself to provide an even more reliable tamper-evident closure. This is achieved by providing a container finish which includes cooperating raised portions which interact with a raised portion on the closure.
While these closures have thus provided commercial products which cannot only provide the tamper-evident function, but which can also visibly demonstrate same, the search has nonetheless continued for even greater improvements in these devices, and most particularly to provide a structure which is fool-proof in connection with highly repetitious operations, and which can at the same time be inexpensively manufactured. It must be recognized in this regard that in applying these closures to bottles or other containers many hundreds of thousands of applications are carried out. It is important, however, that in each case, clean and uniform application of the closure to the container take place, without prematurely fracturing the bridges on the closure, and in a manner such that when the closure is subsequently removed, these bridges will then cleanly and uniformly fracture with relative ease. A failure rate of even a few percent is not an acceptable result in many commercial settings, such as medicinal uses. Until now, reliability has been achieved as a result of manufacturing containers to exact specifications, with a very low tolerance for error. Specifically, bottles have had to be manufactured including an abruptly angled locking bead. The need for such modification in the bottles or containers themselves, however, necessarily results in a significant increase in the manufacturing costs of these tamper-evident containers.